The present invention relates to a method and a device for detecting objects.
A method and a device for detecting objects are used, for example, for pre-crash sensing in a motor vehicle. In this case, a sensor system determines whether a collision with a detected object, for example, another vehicle, may occur. In the case of a collision, it is additionally determined with what speed and at what point of contact the collision will occur. In possession of this information, life-saving milliseconds can be gained for the driver of the vehicle during which preparatory measures, for example, for airbag deployment or for a seatbelt system, can be taken. Other possible applications include parking pilot, blind spot detection, or a stop and go system as an extension of an existing cruise control system (for example ACC, Adaptive Cruise Control).
SAE Paper No. 1999-01-1239 entitled xe2x80x9cRadar-based near distance sensing device for automotive applicationxe2x80x9d by Martin Kunert et al., published at the xe2x80x9cInternational Congress and Exposition, March 1999, Detroitxe2x80x9d describes a radar-based near distance sensor system. The microwave system described therein operates preferably in the 24 GHz frequency range and has at least two sensors one of which covers the front of the vehicle and the other the complete rear part. On the basis of the synthetic antenna aperture resulting from the distributed radar modules, the horizontal angle is determined by triangulation. Each of the individual radar modules has an antenna beam and a flat modular design. A microcontroller performing a variety of functions and ensuring a connection to the vehicle infrastructure, among other things, is also integrated in the radar module. In order to use the triangulation principle, at least two radar modules are required. Due to the limited bandwidth of the radar modules (poor resolution when detecting a plurality of objects) and in order to avoid ambiguous situations, SAE Paper No. 1999-01-1239 describes a configuration that has three radar modules.
An object of the present invention is to provide a method and a device requiring less expensive hardware as compared to conventional methods and devices, while providing reliable detection results.
The object is achieved according to the present invention through a method for detecting objects that has at least two near distance sensors installed on a vehicle with detection ranges that overlap at least partially. The relative positions of possible detected objects with respect to the sensors are determined in the overlap area by the triangulation principle. Possible apparent objects obtained by the object determination are identified using dynamic object monitoring.
By achieving the object of the present invention in this manner, a third near distance sensor such as used in conventional methods and devices is no longer necessary, while reliability of the detection results remains unaffected. Although apparent objects are generated using just two near distance sensors in the overlap area of the sensors by the triangulation principle in the method according to the present invention as in conventional methods, these apparent objects can be identified and eliminated if appropriate by dynamic object monitoring. In an arrangement of more than two sensors, the method according to the present invention has the advantage that fewer sensors are required than would be necessary in conventional methods in order to provide unambiguous measurement results.
It is advantageous that at least the speeds, accelerations, and/or changes in acceleration of the possible detected objects are analyzed for dynamic object monitoring. Using the analysis, it can be verified in a particularly advantageous manner whether the analyzed speeds, accelerations, and/or changes in acceleration of the possible detected objects assume values outside a predefined range of values. In other words, it is verified whether the possible detected objects can be actual detection objects due to their dynamic movements or whether these detected objects are apparent objects.
According to one embodiment of the method according to the present invention, the predefined value ranges are determined according to the respective driving situation and/or are extracted from a memory. Thus the limits of speed, acceleration, and change in acceleration that distinguish a real object from an apparent object are adaptively matched to the driving situation. Thus, Apparent objects are reliably recognized in any driving situation in a particularly advantageous manner.
According to an advantageous embodiment of the method according to the present invention, dynamic object monitoring or dynamic object motions taking place mainly across the alignment of the detection area of the sensors are analyzed. This embodiment advantageously takes into account the fact that the apparent objects, for example in the transverse direction, exhibit unplausible values of speed, acceleration, and change in acceleration.
The object of the present invention also is achieved by a device for detecting objects that includes at least two near distance sensors installed on a vehicle, whose detection ranges overlap at least partially. The device also includes means to determine relative positions of possible detected objects with respect to the sensors in the overlap area by the triangulation principle, and means to identify possible apparent objects obtained by the object determination using dynamic object monitoring. By using means according to the present invention for identifying apparent objects through dynamic object monitoring it is possible in an advantageous manner to implement an object detection system using only two near distance sensors, as well as to achieve a particularly high degree of detection reliability.
The sensors are, for example, pulse radar sensors in the 24 GHz range and are arranged uniformly spaced on the front of the vehicle. The detection range of the sensors is, for example, at least seven meters and the detection angle is, for example, at least 140xc2x0. Through this arrangement of the device according to the present invention, a particularly inexpensive and reliable system is provided that can also be used for different applications. The data delivered using the device according to the present invention can be used at the same time for pre-crash monitoring, for example, while supporting the stop and go function of an adaptive cruise control system (ACC). With respect to the last-named application together with ACC, but also in any other application, it is advantageous if at least one additional sensor system that has a different detection range is also present.